The invention relates generally to electromagnetic clutches for use in motor vehicle powertrain components and more specifically to an electromagnetic clutch having a rotor and armature with an unequal or asymmetric spoke patterns.
The popularity of sport utility vehicles which typically include selectable four-wheel drive systems and other vehicles such as minivans which offer similar part-time four-wheel drive systems have resulted in extensive development work on such systems and improved sophistication thereof. Whereas several years ago part-time, i.e., operator selectable, four-wheel drive systems were typically only utilized in pickup trucks and other vehicles actually likely to be used off-road and on rough terrain, four-wheel drive systems are now provided in vehicles which are outfitted comparably to near luxury vehicles and include as standard equipment such features as power windows, air conditioning, sunroofs, leather seats and sophisticated audio systems. Accompanying such up-market vehicles is an emphasis on smooth and quiet highway performance where such vehicles are most typically utilized.
Accordingly, extensive effort has been expended by purveyors in this field to provide equipment such as transfer cases which satisfy both the mechanical demands of the particular four-wheel drive system as well as the convenience and performance parameters demanded by purchasers of such vehicles. The present invention is directed to an electromagnetic clutch assembly which provides improved smooth and quiet operation.